[PATCH v2] hfs/hfsplus: fix slab-out-of-bounds in hfs_bnode_read_key

[Vasiliy Kovalev]

Syzbot reported an issue in hfs subsystem:

BUG: KASAN: slab-out-of-bounds in memcpy_from_page include/linux/highmem.h:423 [inline]
BUG: KASAN: slab-out-of-bounds in hfs_bnode_read fs/hfs/bnode.c:35 [inline]
BUG: KASAN: slab-out-of-bounds in hfs_bnode_read_key+0x314/0x450 fs/hfs/bnode.c:70
Write of size 94 at addr ffff8880123cd100 by task syz-executor237/5102

Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:488
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 kasan_check_range+0x282/0x290 mm/kasan/generic.c:189
 __asan_memcpy+0x40/0x70 mm/kasan/shadow.c:106
 memcpy_from_page include/linux/highmem.h:423 [inline]
 hfs_bnode_read fs/hfs/bnode.c:35 [inline]
 hfs_bnode_read_key+0x314/0x450 fs/hfs/bnode.c:70
 hfs_brec_insert+0x7f3/0xbd0 fs/hfs/brec.c:159
 hfs_cat_create+0x41d/0xa50 fs/hfs/catalog.c:118
 hfs_mkdir+0x6c/0xe0 fs/hfs/dir.c:232
 vfs_mkdir+0x2f9/0x4f0 fs/namei.c:4257
 do_mkdirat+0x264/0x3a0 fs/namei.c:4280
 __do_sys_mkdir fs/namei.c:4300 [inline]
 __se_sys_mkdir fs/namei.c:4298 [inline]
 __x64_sys_mkdir+0x6c/0x80 fs/namei.c:4298
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbdd6057a99

Add validation for key length in hfs_bnode_read_key to prevent
out-of-bounds memory access. Invalid key lengths, likely caused
by corrupted file system images (potentially due to malformed
data during image generation), now result in clearing the key
buffer, enhancing stability and reliability.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: syzbot+5f3a973ed3dfb85a6683@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=5f3a973ed3dfb85a6683
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Vasiliy Kovalev <kovalev@xxxxxxxxxxxx>
---
v2: add more information to the commit message regarding the purpose of the patch.
---
 fs/hfs/bnode.c     | 6 ++++++
 fs/hfsplus/bnode.c | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/fs/hfs/bnode.c b/fs/hfs/bnode.c
index 6add6ebfef8967..cb823a8a6ba960 100644
--- a/fs/hfs/bnode.c
+++ b/fs/hfs/bnode.c
@@ -67,6 +67,12 @@ void hfs_bnode_read_key(struct hfs_bnode *node, void *key, int off)
 	else
 		key_len = tree->max_key_len + 1;
 
+	if (key_len > sizeof(hfs_btree_key) || key_len < 1) {
+		memset(key, 0, sizeof(hfs_btree_key));
+		pr_err("hfs: Invalid key length: %d\n", key_len);
+		return;
+	}
+
 	hfs_bnode_read(node, key, off, key_len);
 }
 
diff --git a/fs/hfsplus/bnode.c b/fs/hfsplus/bnode.c
index 87974d5e679156..079ea80534f7de 100644
--- a/fs/hfsplus/bnode.c
+++ b/fs/hfsplus/bnode.c
@@ -67,6 +67,12 @@ void hfs_bnode_read_key(struct hfs_bnode *node, void *key, int off)
 	else
 		key_len = tree->max_key_len + 2;
 
+	if (key_len > sizeof(hfsplus_btree_key) || key_len < 1) {
+		memset(key, 0, sizeof(hfsplus_btree_key));
+		pr_err("hfsplus: Invalid key length: %d\n", key_len);
+		return;
+	}
+
 	hfs_bnode_read(node, key, off, key_len);
 }
 
-- 
2.33.8